Up To 3 ADUs and a JADU on Single Family Lots
New ADU Rules Allow More Units
Thanks to brand new HCD guidance and the passage of SB 543 (which just went into effect January 1, 2026), we have explicit confirmation that homeowners with single-family properties can now combine different sections of the law to potentially get three ADUs and a JADU on a single-family property.
In this post, we will show you exactly how the HCD has talked about the statewide ADU code and - rather importantly - how to show that to your city or county.
The important parts of the government code: 66314 and 66323
When we think about going to get ADU permits, we usually start by thinking of AB 66314 which says local agencies have to approve or deny your permit ministerially based on state-wide rules and objective local ordinances that comply with the state-wide government code.
66314 is really robust so a lot of ADUs get permitted that way, but there are still times when a city might have a local restriction that prevents you from getting an ADU permit. A really common occurrence is something like a FAR limit or open space requirement where the city says ‘No you already built up to your maximum square footage on that lot.” When that happened, we would fall back on government code section 66323.
Section 66323 describes a number of different units that cities are required to approve regardless of their local FAR limit and whatnot. So for single family properties, 66323 says you can convert part of an existing structure into an ADU, convert part of the primary home into a JADU and build a new construction ADU under 800 sq ft. And importantly, you can get permits for any combination of these.
The new HCD guidance clarifies that as of January 2026, we can also combine 66314 and 66323.
Can you really use both of these sections together?
When I first heard this, I had to triple check to make sure it was real and sound.
Here is the HCD webinar where I originally heard them speak through this guidance: https://www.youtube.com/watch?v=h52w6E0owb8
And what’s more, a member of our audience at How To ADU spotted a couple technical assistance letters authored by HCD where they specifically explain the legal reasoning behind this combo move.
The first is a letter to Solana Beach where HCD addresses how the city has to allow all combinations of ADUs and JADUs from 66314 AND 66323 together.
In Finding 6, HCD points out:
6. Section 17.02.040 D.4.d. and 5. – Unit Allowance – The Ordinance states, “No more than one junior accessory dwelling unit or one accessory dwelling unit shall be permitted per single-family lot, except as permitted in subsection 5(b) below.” Subsection (5)(b) provides for one detached new construction detached ADU and one junior accessory dwelling unit (JADU). The Ordinance mispresents [sic] State ADU Law.
Government Code section 66323 requires ministerial approval of one JADU, one attached ADU and one new construction ADU within the proposed space of a single-family dwelling, in combination with approval of units subject to section 66314. Senate Bill 543 amends the language of section 66323, effective January 1, 2026, to clarify this requirement: “Notwithstanding Sections 66314 to 66322, inclusive, a local agency shall ministerially approve an application for a building permit within a residential or mixed-use zone to create any of the following units, or any combination of the following units…” (Emphasis added.)
State ADU Law mandates that a local agency “approve or deny” an application under section 66314, and “ministerially approve an application for a building permit within a residential or mixed-use zone” to create the maximum combinations set forth therein. Thus, the City must amend the Ordinance to provide for the allowance of all ADU and JADU combinations described in sections 66323 and 66314.
“The city must…provide for the allowance of all ADU and JADU combinations described in sections 66323 and 66314.”
The letter explains that Section 66323 requires ministerial approval of a JADU, an attached ADU, and a detached new-construction ADU—and crucially—that this must be allowed "in combination with approval of units subject to section 66314." HCD’s conclusion was simple: the City has to update its laws to allow for the dwelling unit combinations set forth in both sections.
In a separate letter to the city of Sacramento, HCD writes again about Unit Format Combinations. Finding 2 from that letter:
2. Section 17.228.105 A – Unit Format Combination – The Municipal Code outlines units subject to local development standards (and thus Government Code section 66314) as being a different category from those subject to section 66323; it then states, “The two options may not be combined,” restricting developable options to only one format of ADU.However, restricting lots to one format is inconsistent with State ADU Law. Section 66317 states that a permitting agency “shall either approve or deny the application to create or serve” an application subject to section 66314, which subdivision (d)(3) states may be “either attached to, or located within, the proposed or existing primary dwelling, including attached garages, storage areas or similar uses, or an accessory structure or detached from the proposed or existing primary dwelling and located on the same lot as the proposed or existing primary dwelling, including detached garages.” Since the statute mandates that a local agency “shall approve or deny” an application under section 66314, while also requiring that “a local agency shall ministerially approve an application for a building permit within a residential or mixed-use zone to create any of the following” under section 66323, the City must amend its Ordinance to allow the full allotment and combination of both 66314 and 66323 units.
HCD’s direct order to Sacramento: "The City must amend its Ordinance to allow the full allotment and combination of both 66314 and 66323 units."
When it comes to convincing your city that this is all true, the HCD is the agency that offers technical assistance to the city. If a city objects to combining 66314 and 66323 ADUs, you can use the HCD ADU portal to request technical assistance for you and your city. Include any communication you received from the local agency, including direct contact information for the staff, and explicitly tell HCD if they have permission to use your project as an example when speaking to the city. Many times, city staff will do what the HCD advises after that initial conversation.
A few years ago, we went through this process to convince cities that they had to allow for any combination of multiple 66323 units and it takes a bit of work but it’s usually worth the time. Some cities may require further work and in those cases, we recommend that you find a land use attorney to evaluate the options for your specific situation (if you haven’t already spoken to one!)
Some thoughts about practicalities
Order probably matters
Some people will not be able to get a permit with 66314, so no big change for them
Some people will explore getting multiple unit permits instead of one larger unit
You have to
Order probably matters
I will only know for sure once homeowners start filing for these combos. But I would bet that there are situations where it will be important to build the 66314 unit first. F
or example, I could imagine using 66314 to build a detached or attached ADU that brings me right up to my FAR limit or an open space requirement limitation. As long as I do the 66314 first, then the 66323s can be built exempt from FAR. But if I did it the other way around, then I might hit my FAR with the 66323 unit and then be denied the 66314 unit.
They can still deny 66314 permits after all!
Some people can’t get a 66314 permit
Along those same lines, I want to be clear that some homeowners can’t get the 66314 ADU permit to begin with. The law allows the city to deny these permits for a number of reasons and that will still be the case.
If you can’t get the 66314 ADU, you are still limited to the combination of different 66323 units and this update in the state code and HCD guidance doesn’t affect you as much.
Who wants this many units?!
Even if you’re reading this and thinking "Ryan, I don’t want 4 apartments in my home and my backyard,” this change may still be relevant to you. Often, I work with homeowners who ask for permits to build two small units instead of one bigger one. This can have advantages in terms of fees, flexibility, or zoning restrictions. I can’t give specific advice for your situation. Instead I’ll just flag that this is a cool update even if you’re not trying to build a whole cottage cluster in your yard.
In addition, I’ll take a moment to say that you should be very careful before getting permits to build this many units on a single family property. There are serious implications to building this many units that will affect the financing options for future home buyers and may affect your own tax liability. If you’re thinking of adding more than one unit, it really makes a lot of sense to speak to lending professionals, realtors, lawyers and other licensed professionals who can give you specific advice for your situation.
The guidance is about what you CAN do - not what you ought to do.
What this might look like
Unit 1: 66314 ADU using local standards (could be attached, detached or conversion)
Unit 2: An ADU converted within an existing space (Section 66323).
Unit 3: A new-construction ADU up to 800 sq. ft. (Section 66323).
Unit 4: A JADU converted within the existing primary (Section 66323).
And SB 9?
HCD also clarified that in some cases you can get an SB 9 unit on top of this. I don’t want to go down that rabbit hole in this article but you can watch their webinar for more information!